418 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



Cricetodipus. Smaller. Ears small, without any lobe to the antitragus. Soles covered 

 with short hairs on the posterior half. Tail rather scantily haired ; not tufted at tip. 

 The species may be arranged under these divisions as follows : 



PEROGNATHUS. 

 A. Tail crested above at the end. 



1. Sides without a lateral fulvous stripe. Size that of Hesperomys leucopus penicillatus. 



B. Tail simple. Sides with a fulvous stripe. 



2. Larger than H. leucopus. Ears large. Above, sandy yellow. Outside of fore 



legs and upper surface of feet white fasciatus. 



3. Size of H. leucopus, or less. Ears small. Hairs very rigid. Above, mixed 

 cinnamon and black. Outside of both fore and hind legs, with the upper 



surfaces of the feet, white Tiispidus. 



4. Rather smaller than the preceding. Ears small. Above, cinnamon and 

 black. Lateral stripe indistinct ; outside of both fore and hind legs like the 



back monticola. 



CRICETODIPUS. 



5. Tail not longer, if as long, as the head and body. Hind foot about one-fourth 



as long as head and body Jlavus. 



6. Tail longer than the head and body. Hind foot more than one-third as long 



as head and body parvus. 



The species of PerognatTius have thus far been found from the lower Eio Grande of Texas to 

 Fort Union, Neb., and westward to the Pacific ocean. 



PEROGNATHUS PENICILLATUS, Woodhouse. 



Perognathu* penidOatut, WOODHOUSE, Pr. A. N. Sc. Phila. VI, Dec. 1852, 200. IB. In Sitgreaves' Expl. Zuui & 



Colorado, 1853, 49 ; plate iii, mammals. 

 AUD. & BACH. N. Am. Quad. HI, 1854, 298. 



BP. Cu. Larger than Ifesperomys leucopus. Ears rather large ; antitragus lobed. Tail longer than the body ; tipper side 

 with a penicillated crest at the extremity. Feet large ; soles naked. Color above yellowish brown. Under parts of body, 

 hind feet, and entire fore legs to shoulder, white. Tail brown, whitish beneath to within an inch of the end ; no fulvous 

 lines on the aides. 



This species is among the largest of the genus, and in many of its characters approaches 

 closely to Dipodomys. It is about the size of Hesperomys leucopus, or larger. The head is 

 broad, depressed, and acute. The muzzle is not cleft beneath, and is densely hairy everywhere, 

 except on the septum and inner margin of the nostrils. The openings of the external cheek 

 pouches are shorter than in P. fasciatus. The whiskers are very long, some of them reaching 

 to the middle of the body. The ears are large for the genus, thin, and sparsely coated with 

 hair ; larger and less hairy than in P. fasciatus. The antitragus is very distinct as a small 

 rounded lobe. The opening of the ear is covered by a tuft of stiff bristly Jiairs. The fur is 

 remarkably coarse and stiff, without any short wool or fur mixed with the longer hairs. The 



